Heat exchanger

ABSTRACT

A heat exchanger ( 20 ) includes a plurality of tubes ( 23 ) with a fluid flowing therein and header tanks ( 21 ) arranged at the longitudinal ends of the tubes ( 23 ) and comunicating with the plurality of the tubes ( 23 ). The header tanks ( 21 ) each include a core plate ( 27 ) coupled with the tubes ( 23 ) and a tank body ( 31 ) coupled to straight portions ( 29 ) holding the joints of the core plate ( 27 ) with the tubes ( 23 ) and forming an internal space of the tank together with the core plate ( 27 ). The cross section of the each header tank ( 21 ) configured of the core plate ( 27 ) and the tank body ( 31 ) is in the shape of an ellipse or a polygon similar to an ellipse, and the aspect ratio of the ellipse inscribed in the cross section of the header tank ( 21 ) is between 0.95 and 1.05 inclusive. Thus, the header tanks of the heat exchanger have a strength capable of sufficiently resisting an increased supercharge pressure.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a heat exchanger having a pair of header tankscapable of having a sufficient strength so as to withstand even ahigh-pressure medium.

2. Description of the Related Art

The restriction of the exhaust gas emitted from large trucks isincreasing more and more every year. At the same time, the superchargepressure and temperature of the intercooler of large trucks haveincreased remarkably as shown in FIG. 9. As a heat exchanger of thisintercooler, a vertically long header tank 11 having a rectangular crosssection shown in FIG. 10 is conventionally known. With the increase insupercharge pressure, however, this header tank 11 is deformed in anincreased amount and may break under an excessively large load imposedon the root of the tubes. An example of this header tank is described inJapanese Unexamined Patent Publication No. 9-196594.

SUMMARY OF THE INVENTION

The object of this invention is to solve the problem described above andprovide a heat exchanger having a header tank capable of sufficientlyresisting an increased supercharge pressure.

In order to solve the aforementioned problem, according to a firstaspect of the invention, there is provided a heat exchanger employing ameans wherein an outside portion of a cross section of the header tanksubstantially perpendicular to a longitudinal direction thereof whichextends from one joint to the other where the tube is connected with thecore plate including the cross section of a tank body is in the shape anellipse or a polygon similar to an ellipse, and wherein the aspect ratioof an ellipse inscribed in the outside portion is between 0.95 and 1.05inclusive. With this heat exchanger, the stress concentration at thejoints between the core plate and the tube can be prevented on the onehand, and the sectional shape of the portion reinforced in strength bythe tubes is not required to be limited on the other hand, therebyimproving the design freedom.

Also, in order to solve the aforementioned problem, according to anotheraspect of the invention, there is provided a heat exchanger wherein thecross section of the header tank substantially perpendicular to alongitudinal direction of the header tank is in the shape of an ellipseor a polygon similar to an ellipse, and the aspect ratio of an ellipseinscribed in the header tank is between 0.93 and 1.05 inclusive.

In this heat exchanger, a header tank is provided in which stressconcentration at the joint between the core plate and the tubes can beprevented, and therefore which has sufficient strength to resist anincreased supercharge pressure.

In order to solve the aforementioned problem, according to still anotheraspect of the invention, there is provided a heat exchanger whereinstraight portions each making up a joint margin are formed at the jointbetween the core plate and the tank body. Therefore, a more reliableheader tank is provided in which the joint area between the core plateand the tank body can be positively secured.

In order to solve the aforementioned problem, according to yet anotheraspect of the invention, there is provided a heat exchanger wherein acap is coupled to the openings at the ends of the cylindrical headertank. When the core plate and the tank body are coupled to each other,therefore, a jig can be inserted from the openings and pressure can beapplied from both inside and outside the header tank, thereby makingpossible a positive coupling.

The reference numeral inserted in parentheses following the name of eachmeans described above indicates an example of correspondence with aspecific means described in the embodiments below.

The present invention may be more fully understood from the descriptionof preferred embodiments of the invention, as set forth below, togetherwith the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view schematically showing a heat exchanger accordingto an embodiment of the invention.

FIG. 2 is a sectional view taken along line A-A in FIG. 1.

FIG. 3 is a diagram showing the relation between the aspect ratio of theinscribed ellipse of the header tank and the stress exerted on the tuberoot.

FIG. 4A is a sectional view showing a header tank including a tank bodyhaving a semicircular cross section and a core plate having a crosssection equivalent to one half of an octagon, wherein the straightportions of the tank body are located outside the straight portions,respectively, of the core plate.

FIG. 4B is a sectional view showing a header tank including a tank bodyhaving a semicircular cross section and a core plate having a crosssection equivalent to one half of an octagon, wherein the straightportions of the tank body are located inside the straight portions,respectively, of the core plate.

FIG. 4C is a sectional view showing a header tank including a tank bodyhaving a semicircular cross section and a core plate having a crosssection equivalent to one half of an octagon, wherein the straightportions of both the tank body and the core plate are extended radiallyoutward.

FIG. 5 is a sectional view of a header tank having an octagonal crosssection.

FIG. 6 is a sectional view showing the shape or a header tank on theside nearer to the tube than the tube root.

FIG. 7 is a perspective view showing a header tank having, at each endthereof, an opening covered with a cap.

FIG. 8A is a perspective view showing a header tank having apseudo-circular outer peripheral portion and an outer peripheral portionlarger in aspect ratio.

FIG. 8B is a sectional view showing a pseudo-circular outer peripheralportion of a header tank also having an peripheral portion larger inaspect ratio.

FIG. 8C is a sectional view showing an outer peripheral portion largerin aspect ratio or a header tank also having a pseudo-circularperipheral portion.

FIG. 9 is a diagram showing recent increases in supercharge pressure andtemperature of the intercooler for large trucks.

FIG. 10 is a sectional view showing a vertically long rectangularconventional header tank.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the invention are explained below with reference to FIGS.1 to 8C.

FIGS. 1 to 6 are diagrams showing a first embodiment of the invention.In FIG. 1, reference numeral 20 designates a heat exchanger. Heatexchanger 20 includes a plurality of tubes 23 with a pair of headertanks 21 juxtaposed at the ends thereof.

The header tanks 21, made of copper, iron or stainless steel high instrength at high temperatures and capable of being processed as a thinmetal sheet, each have a core plate 27 coupled with each tube 23 at tuberoot 25 as shown in FIG. 2. Each core plate 27 has a substantiallysemicircular cross section, and is formed with a straight portion 29 ateach end thereof as a brazing or welding margin. The core plate 27 isalso provided with a Tank body 31 having a substantially semicircularcross section. Tank body 31 also has straight portions 33 as joints withthe core plate 27. The core plate 27 and the tank body are assembledwith the straight portions 29, 33 coupled by brazing and welding,respectively. The header tanks 21 thus assembled are formed in such amanner that the cross section thereof is in contact with an ellipse.

The ellipse 35 inscribed in the cross section of each header tank 21 isexplained in more detail. The inscribed ellipse 35 is assumed to be incontact with an ordinary cross section of the header tank not connectedwith a pipe or a bracket.

Assume that the intersection between the center line E along the centerline of the tube 23 of the header tanks 21 and the inner wall surface ofthe tank body 31 is designated as A, the intersection between the centerline E and the core plate 27 as B and the middle point of the linesegment AB as 0. Also, assume that the intersections between the centerline F passing through the point 0 in the direction perpendicular to thecenter line E and the inner wall surface of the header tank 21 as C, D,respectively. Then, the ellipse having the center at point 0 and one ofthe line segment AB=a and the line segment CD=b as a long axis and theother as a short axis constitutes an inscribed ellipse 35.

The ratio a/b between the long, and short axes of the inscribed ellipse35 is preferably between 0.95 and 1.05 inclusive. The reason for this isshown by way of the graph of FIG. 3. The abscissa represents the aspectratio a/b of the inscribed ellipse, and the ordinate represents themaximum stress exerted on the tube root, assuming that the aspect ratiois 100 when the aspect ratio a/b=1. As can be understood from thisgraph, the maximum stress exerted on the tube root is increased for anaspect ratio a/b of not more than 0.95 or not less than 1.05. As aresult, the plate thickness is required to be increased and themachining becomes difficult, leading to higher costs. Thus, the aspectratio a/b is desirably between 0.95 and 1.05 inclusive.

As stated above, the header tanks 21 or the heat exchanger describedabove have a substantially circular cross section with an aspect ratioa/b of between 0.95 and 1.05 inclusive, and therefore concentration ofstress on the tube root can be prevented. Also, in view of the fact thatthe core plate 27 and the tank body 31 are formed with the straightportions 29, 33, respectively, which are brazed and welded, sufficientcoupling strength is obtained. Even in a high-pressure medium,therefore, sufficient strength can be secured without increasing thethickness, thereby suppressing an increase in weight and cost.

In the case where the inscribed ellipse 35, with a substantiallycircular cross section having the ratio a/b between the long and shortaxes thereof, of not less than 0.95 and not more than 1.05 the thicknessof the heat exchanger is increased, which somewhat disadvantageouslyrequires consideration of the interference with the radiator whenmounted on the vehicle. A vertically long cross section, however, wouldrequire a considerable increase in thickness in order to maintain thestrength, resulting in an increased weight. Therefore, a substantiallycircular cross section can advantageously reduce both the thickness andthe weight, for a lower cost.

FIGS. 4A to 4C and 5 are diagrams showing other examples of the firstembodiment.

FIGS. 4A to 4C showing cross sections of a header tank including asemicircular cross section of the tank body and a half octagonal crosssection of the core plate. The octagonal cross section has the cornersthereof connected at a smooth angle. In the header tank 41 shown in FIG.4A, the straight portions 45 of the tank body 43 are coupled with theoutside of the straight portions 49 of the half octagonal core plate 47.In the header tank 51 shown in FIG. 4E, on the other hand, the straightportions 55 of the tank body 53 are coupled with the inside of thestraight portions 59 of the half octagonal core plate 37. In the headertank 61 shown in FIG. 4C, the straight portions 65, 69 of the tank body63 having a semicircular cross section and the core plate 67 having ahalf octagonal cross section, respectively, extend radially outward, andthe extensions thereof are coupled to each other.

The header tank 71 shown in FIG. 5 is in the shape of an octagonincluding a tank body and a core plate, in which the straight portions75 of the tank body 73 are coupled to the inside of the straightportions 79 of the core plate 77.

The header tanks shown In FIGS. 4A, 4B, 4C, 5 have a cross section inthe shape of a polygon similar to the ellipse or a combination of anellipse and a polygon similar to the ellipse. The polygon, however, isdesirably at least a pentagon. The reason for this is that in the casewhere the polygon has less than five corners, the angle between the tubeand the core plate at the tube root may assume a substantially rightangle as shown in FIG. 10, for increased root stress, depending on theperipheral position of the polygon with respect to the tube. Also, anumber of corners less than 5 would reduce the inside angle of thecorners and concentrate stress.

The portion of the header tank having a cross section In the shape of apolygon similar to an ellipse, therefore, is not necessarily limited toan octagon as in the embodiments described above, but may be a pentagon,a hexagon, a nonagon or a decagon.

Also, the cross section of the header tank portion nearer to the tubethan the tube root is not necessarily in contact with the inscribedcircle. Specifically, as shown in FIG. 6, the portion of the header tank91 nearer to the tube than the tube roots A, B does not necessarilyproject into contact with the inscribed ellipse 35 like the core plate57 of the header tank 51 shown in FIG. 4B, but the tube roots A and Bmats be connected to each other in a region inside the inscribed circle35 like the core plate 93 shown in FIG. 6. This is by reason of the factthat the portion between the tube roots A and B is reinforced by thetube 23 and has sufficient strength without being in contact with theinscribed circle 35.

FIG. 7 is a diagram showing a second embodiment of the invention havinga structure in which an opening 81 is formed at the end of the headertank 51 and covered by a cap 83. By so doing, the tank body 53 and thecore plate 57 can be coupled to each other by inserting a jig from theopening 81 and closely attaching by pressing the straight portions 55,59 against each other from both inside and outside.

Generally, aluminum materials can be welded to each other in spite of asmall clearance which may exist between them. On the other hand, in thecase of a clearance at the weld zone of brass or stainless steel,welding is known to be difficult due to zinc being present in thestructure of the former and due to the oxide film formed on the surfaceof the latter.

In the header tank 51 having the cap 83 according to this embodiment,the welding zone can be closely attached by inserting a jig even whenwelding brass or stainless steel, thereby resulting in highly reliablewelding work.

FIG. 8A shows a header tank 101 according to a third embodiment of theinvention. Header tank 101 includes a similar core plate 57 to the oneshown in FIG. 4B, and the tank body 103 is fixedly welded on the coretank 57. The tank body 103 has first tank outer peripheral portions 153having a pseudo-circular cross section (aspect ratio of 1.95 to 1.05) asshown in FIG. 8B, and second tank outer peripheral portions 105 having alarger aspect ratio (1.2, for example) than the first tank outerperipheral portion 153 as shown in FIG. 8C. The first tank outerperipheral portions 152 and the second tank outer peripheral portions105 alternate with each other to thereby form the tank body 103.

In view of the fact that the tank body 103 of the header tank 101 hasthe first tank outer peripheral portions 153 having a pseudo-circularcross section (aspect ratio of 1.95 to 1.05) and the second tank outerperipheral portions 105 having a larger aspect ratio (1.2, for example)than the first tank outer peripheral portions 153, as described above,the rigidity of the tank as a whole is improved and deformation thereofsuppressed, thereby reducing root stress.

The shapes of the first tank outer peripheral portions 153 and thesecond tank outer peripheral portions 105 are applicable to the commonportion other than where a pipe, a mounting bracket, etc. are arranged.Also, the aspect ratio of the shape of the second tank outer peripheralportions 10 is not limited to and can assume any value other than 1.2.

While the invention has been described by reference to specificembodiments chosen for purposes of illustration, it should be apparentthat numerous modifications could be made thereto by those skilled inthe art without departing from the basic concept and scope of theinvention.

1. A heat exchanger comprising: a plurality of tubes, a fluid flowstherein; and a pair of header tanks arranged at the longitudinal ends ofthe tubes and communicating with the plurality of the tubes, the headertanks each including: a core plate having both ends portion betweenwhich the plurality of tubes are connected with the core plate, and atank body coupled to the end portions of the core plate, thereby formingan internal space of the tank together with the core plate; and whereinan outside portion of a cross section of the header tank substantiallyperpendicular to a longitudinal direction of each header tank whichextends from one to the other of joints where the tube is connected withthe core plate including the cross section of the tank body is in theshape of an ellipse, or a polygon similar to an ellipse, and wherein theaspect ratio of the ellipse inscribed in the outside portion is between0.95 and 1.05 inclusive.
 2. A heat exchanger according to claim 1,wherein joints between the core plate and the tank body are formed witha straight portion, constituting a joint margin.
 3. A heat exchangeraccording to claim 1, wherein the header tank has end openings coupledwith a cap.
 4. A heat exchanger comprising: a plurality of tubes a fluidflows therein; and a pair of header tanks arranged at the longitudinalends of the tubes and communicating with the plurality of the tubes, theheader tanks each including: a core plate having both ends portionbetween which the plurality of tubes are connected with the core plate,and a tank body coupled to the end portions of the core plate, therebyforming an internal space of the tank together with the core plate; andwherein a cross section of the header tank substantiality perpendicularto a longitudinal direction of the header tank is in the shape of anellipse or a polygon similar to an ellipse, and wherein the aspect ratioof the ellipse inscribed in the header tank is between 0.95 and 1.05inclusive.
 5. A heat exchanger according to claim 4, wherein jointsbetween the core plate and the tank body are formed with a straightportion constituting a joint margin.
 6. A heat exchanger according toclaim 4, wherein the header tank has an openings coupled with a cap.